Improved diesel fuel



Patented Dec. 26, 1939 UNITED STATES 2,195,157 nurnovan DIESEL rum.

Edwin M. Nygaard and George S. C'randall, Woodbury, N. J., assignors toSocony-Vacnum Oil Company, Incorporated, New York, N. Y., a corporationof New York No Drawing.

2 Claims.

This invention "relates to fuels for internal combustion engines of thecompression ignition or Diesel type and is more particularly concernedwith the modification or control of the combusll tion characteristics ofliquid hydrocarbon fuels, which are normally used in Diesel engines, bythe addition to such fuels of a novel characterizing ingredient.

As is well known to those'familiar with the art, the requirements of aDiesel cycle engine call for a fuel whose ignition and combustioncharacteristics are opposite to those normally required by a fuel for anengine operating on the Otto cycle, the latter engines being typified bythe ordinary spark ignition gasoline engine.

The combustion desired in a spark ignition engine is characterized bycontrolled or controllable slowness of fuel ignition, too rapid ignitiongiving rise to the phenomenon known as "knocking. In an engine operatingon the Diesel cycle, on the other hand, enhanced speed of ignition isdesired, since the fuel is injected into the combustion space and mayexert maximum efficiency only when the delay period between injectionand ignition is short.

In 9. Diesel engine, therefore, improperly delayed ignition causesknocking, the reason for such knocking being the reverse for that in anOtto cycle engine. It will be seen, therefore,

90 that a fuel having combustion characteristics which are mostdesirable for an Otto cycle engine is for this reason not desirable foruse in a Diesel engine. Likewise, an addition agent which is normallyconsidered to improve the 88 combustion characteristics of a fuel for anOtto cycle engine is not considered desirable for use 2. Diesel cycle.

' This invention has to do specifically with fuels for Diesel enginesand has for its primary object 40 the development of a method foraccelerating the spontaneous ignition of liquid hydrocarbon fuels incompression ignition engines, which method is characterized by theadmixture .of tetranitro methane with the fuel prior to its ignition.

4g Tetranitro methane is a compound having the probable empiricalformula C(NOzM. which is well known to the art,.and may be prepared byvarious published methods illustrative of which are the following:

60 (a) By the'action of fuming nitric acid in concentrated sulfuric acidon nitrofo'rm (see Schischkofi', Ann. 119, 248, (1861)).

(b) By the action of silver nitrite'on iodonitromethane (see Hantzch,Ber. 39, 2479 (1906)).

(c) By extensive nitration of aromatic hydro- Application November 30,1938, Serial No. 243.117

carbons or their nitro derivatives with nitrosyi sulfuric acid (seeClaessen, D. R. P. 184, 229, Centralblatt .1907, II, 366).

((1) By the action of diacetyl orthonitric acid or fuming nitric acid onacetic anhydride 6 (Pictet, Genequand Ber. 36, 2225, (1903), Pictet,Khotinsky, Compt. rend. 144, 211, (1907); Ber. 40, 1164 (1907)).

(e) By the action of nitrogen 'pentoxide on acetic anhydride (Schenk, D.R. P. 211, 198 and 10 211, 199, Centralblatt, 1909, II, 81).

(I) By the action of nitric acid (D=1.53) on acetic anhydride,(Chattaway, J. Chem. Soc. 97, 2099 (1910)).

In demonstrating the value of tetranitro methane as an improver of theignition quality of 9. Diesel fuel, we have prepared this compound bythe method of Chattaway referred to under Example (j) above and haveprepared a blend of 0.5 per cent tetranitro methane inya base stock ofthe type commonly known as No. 2 fuel oil, which had a flash point of156 F., specific gravity of 0.86 and a Lovibond color of 0.25. The

ignition quality of the base stock and the fuel blend was determinedbycomparison with a standard reference fuel in a converted C. F. R.engine, using the ignition delay method. The value obtained in this testis expressed as the cetane number, which is the per cent by volume ofcetane in a blend of,cetane and alpha methyl naphthalene having the samecombustion characteristics as the sample under test, (see Proc. Am. Soc.Testing Materials, volume 36, I, 418 (1936)).

The cetane number of the base stock used in this test was 42 and that ofthe 0.5 per cent blend of tetranitro methane in the same base stock was'49. Thus, the ignition quality of the fuel was increased seven cetanenumbers by the admixture with the fuel of only 0.5 per cent tetranitromethane prior to its ignition.

Tetranitro methane may be used in the method contemplated by thisinvention in amounts varying from about 0.1'per cent to about 5.0 percent, and it is to be understood that when the term "Diesel fuel, Dieseltype fuel, or liquid hydrocarbon fuel, etc, are used herein, we havereference to any liquid hydrocarbon adapted for use in any compressionignition engine.

We claim:

1. The method of accelerating the ignition of liquid fuels in aninternal combustion engine of the type wherein ignition of the fuel isspontaneously eflected by injection into the compressed air in theengine cylinder which comprises ad- 66 mixing with the fuel .prior toignition a minor proportion of tetranitro methane. v

2. The method of accelerating the ignition of liquid fuels in aninternal combustion engine of 5 the type wherein ignition of the fuel isspontaneously effected by inJection into the compressed air in theengine cylinder which comprises admixing with the fuel prior to ignitionabout 0.5 per cent of tetranitro methane.

EDW'DI M. NY GAARD. I GEORGE S. CRANDALI

